Oxidized starch-protein composition and methods for producing and using the same



Nov. 19, 1968 G. E. LAUTERBACH 3,411,925

OXIDIZED SIARCH-PROTEIN COMPOSITION AND METHODS FOR PRODUCING AND USINGTHE SAME Filed March 24, 1966 3 Sheets-Sheet 1 BINDER COMPONENT WATEROXIDIZING ALKALI (COMMON STARCH PLUS AGENT AT LEAST 5% PROTEIN) 6P TIoTI/TI SOAP COOK AT TEMPERATURE OF 220-350F UNDER PRESSURE COMPOSIHON ATTEMPERATURE OF ABOUT l80-200F I *1 I COATING COMPOSITION I I ICOMPONENTS INCLUDING I l I f J L OPTIONAL l COATING I COMPOSITION I lFIG. 1

1968 G. E. LAUTERBACH 3,411,925

OXIDIZED STARCH-PROIZiN COMPOSITION AND METHODS FOR PRODUCING AND USINGTHE SAME Filed March 24, 1966 5 Sheets-Sheet 2 4 l0 7 5 ll l 8 .vvAl

FIG. 3

TO RECEIVING ZONE N v. 19, 1963 G. E; LAUTERBACH 3,411,925

OXIDIZED STARCH-PROTEIN COMPOSITION AND METHODS FOR PRODUCING AND USINGTHE SAME Filed March 24, 1966 3 Sheets-Sheet C- STARCH PROTEIN VISCOSITYCHARACTERISTICS IOO..

so. so.

VISCOSITY IO z '1 I 0 IO 20 3O 4O 5O 6O 7O 8O 90 I00 PROTEIN BY WEIGHTFIG. 5

United States Patent 3,411,925 OXIDIZED STARCH-PROTEIN COMPOSITION ANDMETHODS FOR PRODUCING AND USING THE SAME George E. Lauterbach, Neenah,Wis., assignor to Kimberly-Clark Corporation, Neenah, Wis., acorporation of Delaware Continuation-impart of application Ser. No.291,825, July 1, 1963. This application Mar. 24, 1966, Ser. No. 543,446

11 Claims. (Cl. 106-157) This application is a continuation-in-part ofmy copending application Ser. No. 291,825 filed July 1, 1963, nowabandoned and assigned to the same assignee.

This invention relates to the production of a starchprotein producthaving various utilities, and to paper coating compositions and coatedpaper which include such products as a binder.

This application is related to my co-pending application Ser. No.116,734 filed June 13, 1961, now Patent No. 3,211,564, and assigned tothe same assignee as the present invention. In that application I havedescribed the substantially continuous coordinated production of acoating composition by means which included effecting controlled cookingand modification of raw or common starch at temperatures Well above thegelationization range of the starch in the presence of an oxidizingagent which is consumed in the process. I have now found that, whenprotein is incorporated with the common starch and oxidizing agent underalkaline conditions, a beneficial product is attained which isparticularly useful in coating compositions for paper.

For convenience of illustration the invention is specifically describedin connection with the formulation and use of the starch-protein productas a binder in aqueous emulsion mineral containing coating compositionsfor light basis weight printing papers.

It has been suggested to produce coated printing papers with aqueousemulsion coating systems. Such systems have included in the dispersionphase an oil which volatilizes at a higher temperature than the water ofthe emulsion. The dried coating exhibits a multiplicity of voids createdby the vaporization of oil in drying which voids contribute to theopacity of the coated paper. Primary difficulties with such systems havebeen the expensive nature of the binder component, the tendency of thecompleted coating to be tacky to the touch and for letterpress printingpaper the necessity of a high pick resistance.

A primary object of the invention is to provide a novel starch-proteinfluid composition.

A principal object of this invention is to provide an aqueous coatingcomposition emulsion which contains a significant quantity of pigmentand employs a binder material which is economical and is formulatedprincipally from native or common starch and protein subjected to anoxidizing action in the presence of each other.

Another object of the invention is to provide a coated printing paperwhich is of improved resistance to the development of tack when exposedto the touch of a finger, for example.

A particular object of the invention is to provide a novel method ofproducing a starch-protein product having utility as an adhesive andwhich method involves subjecting the common starch and protein to anoxidation reaction in an aqueous slurry of the protein and starch.

An important object of the invention is to provide a starch-proteinproduct useful as a binder and which may be derived from common flourscontaining starch and protein without addition of other starch orproteinaceous components.

In the preferred practice of the invention common 3,411,925 PatentedNov. 19, 1968 "ice starch preferably has incorporated therewith a smallproportion by weight of a proteinaceous material, and the starch andprotein are cooked and modified (oxidized) together. This cooking andmodification takes place under pressure in a distinctly alkaline aqueoussystem with agitation at elevated temperatures (220-350 F.) in thepresence of a small quantity of an oxidizing agent which forms mainlycarbonyl from the alcohol groups of starch. Although the reactions whichtake place during the cooking and modification are not completelyunderstood and my invention is not predicated on any particular theory,a possible explanation of the factors involved is offered. Apparentlythe elevated temperatures and agitation cause the starch and protein toswell quickly and to disperse essentially molecularly and approach atrue solution form. Under the influence of the alkaline and oxidizingagents which permeate the material, oxidizing the protein and starch,interaction between the protein and starch results. The interactionapparently achieves a branching of some of the molecules of the starchby grafting protein molecules thereto.

This interaction is not affected by the presence of other usual papercoating components of mineral paper coating compositions; the systeminteraction is, however, characterized by a high alkaline requirementfor paper coating compositions during cooking and modification(oxidation)much greater than is normally required to offset the acidicsubstances produced in the starch modification. The protein apparentlyundergoes hydrolysis as well as oxidation. This alkaline hydrolysisresults in the production of acidic products which may be offset by theincreased alkali added to the system. Also, the globular shape of theprotein molecule is apparently changed to a more linear form.

Whatever be the explanation,I have found it essential to the practice ofthe invention that the cooking of the starch and protein together withthe agent which forms the carbonyl groups from the alcohol groups ofstarch be effected rapidly at a temperature well above thegelatiniz-ation range of the starch. The starch used preferably iscornstarch, termed in the trade pearl starch, but may be potato, wheat,rice, or tapioca starch, for example. Also, the protein may take anynumber of convenient forms such as soy protein, casein and the like. Aparticular feature of the invention is that the common starch andprotein may be included in one component such as sorghum or corn orwheat flour. In this application the term common starch is intended toinclude the thick boiling unmodified starches although in the industryreference is frequently made to all of such raw starches as pear starch.

Most important to the production of a suitable paper coating compositionis that the binder system have little tendency to gel upon cooling. Somestarches, such as those which are substantially free of amylose as waxycorn, white sorghum and the like are adequate in this respect but arepresently more expensive than the preferred native or common starchesavailable on the open market. I have found that the gelling tendency ofstarches such as potato, tapioca, corn, wheat, rice and sorghum may becontrolled adequately by the inclusion within the composition of soap tothe extent of about 0.75% to 1.25% based on the dry binder weight.Particularly, it appears that the quantity of soap is relativelycritical and optimum results are achieved at about 0.9% to 1% binderweight. The soap should be added to the extent that maximum thinning ofthe binder composition occurs. The soap is not necessarily added to thecomposition before cooking. It may be added to the hot materialemanating from the cooker but should be added before cooling to preventgelatin. Preferably, the soap is cooked with the starch and protein.

The oxidizing agent which is required to be added to the starch-proteincomposition in the cooker may be added to the extent of about 0.1% to 5%by weight of the binder. The quantity is selected so that the oxidizingagent is essentially completely exhausted during the reaction and thequantity is proportioned to the starch and protein to achieve apredetermined viscosity under the temperature conditions of thereaction. The oxidizing agent is further selected to be dispersible inan aqueous alkaline starch slurry and is required to be soluble in waterto a considerable degree. Persulfuric acid and soluble salts thereofsuch as ammonium persulfate have been found to be particularly suitable,but other hydrolyzing agents such as the hypochlorites, peroxides, andothers may be employed. The utility of the oxidizing agent variessomewhat depending upon the ultimate use of the starchprotein reactionproduct, as some agents cause color formation in the final composition.The amount of oxidizing agent required is small, having an insignificanteffect on total solids of the composition and is, in fact, dependentupon the selected reaction temperature and the extent to which themodification of the starch and protein is desired for the particularcoating composition solids. At higher temperatures less oxidizing agentis required to effect a given viscosity change in the common (raw)starch and protein.

The aqueous dispersion of the protein-starch-oxidizing agent isnecessarily made distinctly alkaline for paper coating composition usageso that the final composition preferably has a pH in the range of 8 to10. Any common alkali such as sodium hydroxide, sodium bicarbonate,sodium carbonate, sodium tripolyphosphate, tetrasodium pyrophosphate orthe like serves the purpose.

The protein must, for my purposes, be cooked and oxidized with thecommon starch; separate cooking and oxidation of the protein and starchdo not result in coating formulations of the same quality. Commonly,when starch and protein are simply cooked separately in the presence ofan alkali, the viscosity of each dispersion is relatively high. Wheneach is cooked in the presence of both an alkali and an oxidizing agent,the viscosity of each is much lower. Quite unexpectedly, I have foundthat by cooking and oxidizing the starch and protein together at atemperature in excess of the gelatinization range of the starch, theviscosity is materially higher than in the latter of the foregoinginstances.

The cooking and oxidation of the common starch and protein may takeplace in equipment and under conditions as set forth in my co-pendingapplication Ser. No. 116,734 filed June 13, 1961, now Patent No.3,211,564. Thus, the cooking may most conveniently be effected in a jetcooker, or a Ther-mutator (a product of Cherry- Burrell Company, CedarRapids, Iowa), the latter being essentially a continuous autoclave. Suchcookers provide for the cooking and oxidation actions and starchproteininteraction in a minimal time.

The temperature of cooking and modification must be above the gelationrange of the starch employed. Temperatures of 220-350 F. have been foundmost useful in effecting control of the process as to viscosity andcompletion of the oxidizing action on the starch and protein within ashort period of time. Such tempera tures are well above thegelatinization range of most common starches used in paper coatingcompositions, starches commonly having a gelatinaztion range betweenabout 120175 F. The reaction time at these high temperatures (220350 F.)must be maintained short in order to obtain maximum control of theoxidation step by consumption of the oxidizing reagent under controlledconditions, and for this reason a continuous cooking and oxidizingprocess is preferred.

Necessary to the formation of an adequate paper coating compositionwhether it be a conventional composition or of the aqueous emulsion typeis the inclusion of some pigment. Such is not a specific feature of thepresent invention but has been found to be highly desirable foreffective drying of emulsion coating compositions and volatilization ofthe oil from the web. This pigment may be clay, calcium carbonate,titanium dioxide or the like, that is,-any conventional aqueous papercoating composition pigment. However, clay is preferred for reasons ofeconomy. The clay may itself be added to the aqueous starch-proteindispersion and cooked therewith, and this is desirable as it aids claydispersion. However, if preferred, the clay may be added after thecooking and modification of the starch and protein. ,In the emulsionpaper coating compositions, particularly for letterpress printing, theproportion of binder to pigment is somewhat greater than in conventionalmineral pigment coating compositions wherein the pigment is customarilythe dominant component on a weight basis.

In general, in paper coating compositions of an oil-inwater nature, thesolids content of the total composition is in the range of about 25 toabout 45%. For letterpress printing the ratio of binder to pigment ortotal solids as well as the binder to oil ratio are important factors inthe production of an adequate coating. The following data are predicatedon a dry basis with the protein content included as binder since itserves this function as well as that of emulsifying agent. Based on anoil having a specific gravity of 0.78, the binder to oil weight ratio issuitably between about 1:1 to 1:2.25, and the pigment to binder ratiofrom about 1:1 to about 1:1.4. The coating composition viscosity ispreferably between about 3,000 to 18,000 centipoises, as measured on aBrookfield viscometer at 50 C. at rpm. with a #6- or #7 spindle.Further, the protein in such oilin-water systems preferably constitutes510% of the total binder weight. For rotogravure printing paper theprotein of the oil-in-water system may form a larger proportion of thebinder. The oil content of itself is not critical to cell or voidformation but the oil content does bear a relationship to the pigmentand binder content in the production of numerous cells of adequatedimension for uniform light reflectance from the finished coated web. Ingeneral, the proportions of oil, pigment and binder, when employing thestarch-protein product as a binder, are not in themselves a specificfeature of this invention.

Oil addition for aqueous emulsion coating composition formulation may bewith the starch-protein so that the oil passes through the cooker, orthe oil may be added to the hot composition after cooking. In any event,it is desirable to add the oil while the composition is in a state ofrelatively low viscosity. Useful oils must be immiscible with water andinclude those such as kerosene, Stoddard solvent, xylene, Stanisol andthe like having a higher boiling point than water at the coatingcomposition drying temperature so that, upon drying of the coating, theprimary portion of the oil is volatilized after the water has beenessentially completely removed.

The invention will be more fully understood with respect to thefollowing detailed illustrative examples and the accompanying drawingswherein:

FIG. 1 is a flow chart illustrating a preferred embodiment of the methodof invention including optional steps for addition of coatingcomposition components;

FIG. 2 is :a fragmentary view in cross-section of a coated productproduced in accordance with the invention;

FIG. 3 is a view of an apparatus arrangement for effecting the process;

FIG. 4 is a fragmentary view of a modified form of apparatus illustratedin FIG. 3 and particularly adapted for cooking of a coating compositionwith oil inclusion; and

FIG. 5 is a graph illustrating the viscosity relationship ofcompositions of starch-protein cooked and oxidized in accordance withthe present invention as contrasted with conventional methods.

Referring first to FIG. 3 of the drawings, the numeral 1 designates alongitudinally extending mixing chamber having an outlet 2 at itsrightward end. This chamber is preferably of stainless steel and ofcircular cross section. At its leftward extremity 3 the chamber 1 isthreadedly received in a holder 4 which is adapted to retain an orificeplate 5 supported in a cavity 6 of the holder in abutment within aninternal peripheral shoulder 7 of the holder. The plate 5 is itselfprovided with a plurality of peripherially disposed orifices 8 whichangle and open toward the longitudinal axis of the mixing chamber. Plate5 is supported at one extremity 9 of a longitudinally axially extendingstainless steel conduit 10 of small diameter. At its rightward extremity9 the conduit 10 opens axially into the mixing chamber 1. Leftwardly theholder 4 receives threadedly an adapter 11 which is axially bored at 12.Conduit 10 extends through the adapter. A steam inlet 13 extendsthroughout holder 4 and communicates with a steam chamber 14. Thus,communication is established for the flow of steam through the inlet 13,steam chamber 14, and angled orifices 8 to the mixing chamber 1. Aplurality of such orifices, two of which are illustrated in FIG. 3, maybe provided in the plate 5, and an efficient system is to dispose theorifices approximately 90 apart around the orifice plate 5. The leftwardextremity 15 of the conduit 10 is adapted to receive a flow of theslurry to be mixed and cooked in the chamber 1. The described systemprovides for thorough agitation and shear of the slurry under theinfluence of the steam issuing from the orifice plates. In conventionaloperation, a flow of gallons per minute through the mixing chamber 1,depending upon unit size, is quite feasible.

In broad aspect the compositions formulated as in FIGS. 1 and 2 are fedto the conduit 10 through the inlet extremity 15 to the chamber 1.Simultaneously, the steam entering the inlet 13 and directed toward theaxis of the chamber 1 causes material agitation of the slurry, swellingand granular rupture of the starch, as well as swelling of the protein,and exposes these latter components to the action of the oxidizing agentin the slurry. The cooked and modified material presses continuouslyfrom the outlet 2 to a receiving tank and is either in the form of anadhesive composition or as a complete paper coating composition. Asindicated in FIGS. 1 and 2, the addition of components either before thecooking or after the cooking to provide a paper coating composition isoptional. However, such latter formulations are pertinent to theinvention, since they result in materially improved coatingcompositions. Particularly is this so when one of the added componentsis oil to produce an emulsion. The oil itself may be added to the slurryflowing through the conduit 10 via inlet 16 as indicated in FIG. 4, ifso desired. Generally, however, the oil is added to the hot compositionwhich emanates from the chamber 1 as less vapor losses result.

In FIG. 5 the viscosities of starch-protein dispersions produced inaccordance with this invention (curve designated 3) are compared withthe viscosities of starchprotein dispersions in which (a) the commonstarch and protein are each cooked and modified separately with ammoniumpersulfate, and (b) a commercially modified starch and protein (deltalow viscosity) are cooked separately.

The data for curve 3 were obtained by cooking and oxidizing the commonstarch-protein dispersions at 260 F. in an alkaline aqueous solutioncontaining 1% of ammonium persulfate based on the weight of thestarchprotein and 1% soap based on the starch weight. For the data ofcurve 1 the starch and protein were cooked and modified separately inalkaline solution at 260 F. in the jet cooker with ammonium persulfatepresent again to the extent of 1% on the weight of the component and, inthe case of starch, with 1% soap on the starch weight. The data forcurve 2 were obtained by cooking protein 6. at 60 C. in alkalinesolution and separately cooking the commercially modified starch for 15minutes at C.

The comparison is made at 12% solids at about pH 9 at a temperature of50 C., the viscosities being in centipoises as measured with aBrookfield viscometer at rpm. and an appropriate spindle (No. 1 or No.2), and over the range from about zero percent protein to 90% protein.As will be noted, the viscosities of the compositions (semi-log scale)indicated in subparagraphs (a) and (b) above, and designated as curves 1and 2 respectively, are materially lower throughout the protein rangewhen protein is present even in very slight amount. Further, betweenabout 5% and 10% protein (curve 3), in which the protein serves mostbeneficially in the production of adhesives for letterpress printingpaper, the viscosity differences are very considerable. The sharp risein curve 3, I consider, is a result of the starch-protein interaction.As the protein content increases beyond about 50%, the viscositydecreases due to the reduced starch quantity in the system. However, itis to be noted that, as the starch content decreases to about 50%, theviscosity continues to rise. While high protein contents, 70-85%, asevidenced by the curve designated 3, give corresponding viscosities tothe 5-10% protein, the former range is much more expensive for coatingcompositions and will not provide the desired adhesive strength forletterpress printing paper. In most paper coating composition usages itis desirable to have the protein content below about 50% and below about10% for letterpress printing paper.

The following specific examples illustrate the novel procedures ingreater detail. The experimental results are indicated in theaccompanying table. In each instance the coating formulation is appliedto a 28-pound basis weight (25" x 38" x 500 sheets) publication gradebase paper by means of a blade coater unless otherwise indicated. Suchbase paper contains about 40% bleached sulfite pulp by weight and 60%bleached ground wood (dry basis). In each instance the coatingcompositions applied to the web were dried in a blast of hot air andthen lightly supercalendered. The final cooled product is illustrated inFIG. 2 wherein the numeral 18 designates the paper web, 19 a coating oneach side of the paper, and 20 indicates the cells formed by evolutionof the oil during drying.

EXAMPLE 1 Water 2700 Sodium carbonate 16 Starch, pearl corn (10%moisture) 1080 Protein, soya (7% moisture) Ammonium persulfate 9 Theabove composition was cooked at a temperature of approximately 260 F.and the composition was flowed through the cooking apparatus at a rateof approximately /2 gallon per minute. This composition, with 10 partsof soap added and if reduced to about 12% solids by the addition ofwater, is suitable for use as a size in paper treatment and provides inthe usage reduced water penetration as compared to starch sizes asusually prepared. In the present instance, however, a complete coatingcomposition was formulated as follows. As the composition issued fromthe cooking and oxidizing chamber to a suitable mixing tank (not shown)some water was lost as steam in flash-off, but since condensate is addedin the steam cooker, the cooked, oxidized composition is only slightlydiluted. The composition appears as a readily flowable mass. To thecomposition there is then added while agitating about 7 parts of a 50%aqueous solution of NaOH, 1200 parts by Weight of clay and about 10parts by weight of sodium stearate. After blending in of this pigment,soap and alkali, the temperature of the coating composition is stillquite high, approximately 200 F. About 1782 parts by weight of oil (S.G.0.78) and then blended into the composition. Additionally, water isadded in sufficient amount to provide a viscosity of 7,000 centipoisesand a solids content of 28.5%. Such additions cool the composition toabout 150 F. This entire mixture is then treated in suitable emulsifyingequipment (while at about 150 F.) to thoroughly disperse the oil in theaqueous phase as very small droplets having a diameter on the average ofbetween about 0.5 and 3 microns. The emulsification is effected easilyand should be continued until at least about 95% of the droplets arewithin the stated range as such leads to good optical properties in thedried coating composition on the paper web.

The cOating composition is permitted to cool to approximately 140 F. andis then applied to the web by a laboratory blade coater. The coating isquickly dried by directing a blast of high temperature air at about 300F. directly to the coated surface of the sheet. The coating dries inless than about 1 second. The second side of the sheet may then besimilarly coated and dried. The coated web is then lightlysupercalendered. Data indicating the characteristics of such web coatedone side are shown in Table I.

EXAMPLE 2 This example illustrates a coating composition havingcomponents similar to that of Example 1 but prepared on papermillequipment and coated on to the paper web in an experimental mill run.The composition fed to the cooker unit contained the following.

Parts by weight The above composition was cooked at about 260 F. andissued from the cooker at a rate of about 5 gallons per minute. 170parts by weight of oil (Stoddard solvent) and 150 pounds of water wereadded to the hot composition (temperature about 170 F.), the oil beingblended in by means of vigorous agitation. The composition, while stillhot (150 F.), was treated in a Kady mill to improve emulsification. Theresulting composition had a viscosity of 70 poises at 50 C. as measuredon a Brookfield viscometer with a No. 6 spindle at 100 rpm. Thecomposition was applied to one side of a 28-pound web, dried, thenapplied to the second side and dried. The application was made with aChampflex coater, that is, a reversely rotating small diameter rod toremove applied excess coating. The coated web was then dried in a blastof hot air (300 F.) and lightly supercalendered on a productionsupercalender. The characteristics of the supercalendered web for thetwo side coating application are shown in Table I.

EXAMPLE 3 The present example, which is divided into two parts,illustrates the effect of differing quantities of protein atsubstantially the same binder level with all other components remainingthe same. A composition having the following components was prepared andpassed through a laboratory jet cooker.

Parts by Weight Comp. A Comp. B

In the first of the above compositions the protein forms 10% of thetotal binder while, in Composition B, the pro tein is about 5% of thetotal binder. Each of the compositions was passed through a jet cookerat a temperature of about 260 F. Oil and water were then added. The oilwas added first to the compositions while at a temperature of about180200 F., and the quantity of oil in each instance was about 1782 partsby weight (5.6. 0.78). This oil quantity is about 312 parts by weightfor each 400 parts by weight of dry solids. In each instance the oil wasblended in with vigorous agitation and water was added to achieve aviscosity of about 130 poises. The percent solids under such conditionsof Composition A was 29.6 and the percent solids of Composition B, 31.6.The final pH was 9.1 for Composition A and 8.6 for Composition B. Eachof the compositions was applied to a paper web of the nature previouslydescribed on a laboratory rod coater and the coatings were then dried ina blast of hot air having a temperature of about 300 F. The drying ofthe coatings is effected in less than 1 second. Each dried coated webwas then lightly supercalendered. Table I indicates the characteristicsof the coatings for coated one side paper and it will be noted therefromthat in each instance the letterpress pick and the half tone values, aswell as the opacity and brightness, are quite satisfactory forletterpress printing papers.

While the comparison set forth has been made at a coat weight per sideof 3% pounds (dry basis), coat weights of less than 3 pounds are quitesuitable. For ex ample, a coat weight of 2.9 pounds using the 5% proteinon the total binder weight exhibited a letterpress pick of 1, an opacityof about 88, and a brightness in excess of 69. If the quantity ofprotein is reduced below about 5%, then emulsion formation becomes moredifficult and requires an excessive amount of power to accomplish thesame degree of oil dispersion. Above about 10% protein the compositionbecomes more expensive without imparting to the finished coated webmaterially improved characteristics desired in letterpress printing and,accordingly, such extensive use of protein is not commercially warrantedfor this purpose.

EXAMPLE 4 p Protein (delta low viscosity soya-7% water) 480 Sodiumhydroxide, aqueous solution 12 Soap (sodium stearate) 43.2 Ammoniumpersulfate 39.2 Ammonium hydroxide 144 Sodium hexametaphosphate 9.6Water 9300 Oil was pumped into this slurry through inlet 16, the oilbeing added in excess.

This oil-containing composition was cooked at a temperature ofapproximately 260 F. and, upon emanating from the cooker, was useful asa coating composition without further treatment of any kind. Theemulsion which formed was not as fine as in emulsions formed inhomogenizing equipment but was definitely useful. This complete coatingcomposition had a pH of 8.1 and a percent solids of 29.8, and containedabout 432 parts by weight of oil (S.G. 0.78) per 400 parts of solids.When applied to a paper web to the extent of about 3 pounds per side,dried in the hot air blast at a temperature of about 300 F. and thenlightly 'supercalendered, the coated web had the characteristicsindicated in Table I.

EXAMPLE 5 The following example illustrates the use of soya bean flouras the protein component. A composition was formulated as follows:

Parts by weight Clay (papermakers coating) 1200 Starch, pearl cornwater) 1080 Soya flour (about 7% moisture) 240 Ammonium hydroxide (50%aqueous solution) 10 Soap (sodium stearate) 10 Ammonium persulfate 9Sodium hexametaphospate 2.4

Water 2700 EXAMPLE 6 The effect of the quantity of the oxidizing agenton ultimate viscosity is illustrated by the following comparative tests.The compositions were identical except that in Composition A the amountof oxidizing reagent was twice that of Composition B. The compositionswere as follows.

Parts by Weight Comp. A Comp. B

Clay (papermakers coating) 1, 200 1, 200 Starch, pearl corn (10%moisture)-.- 1, 080 1, 080 Protein, delta low viscosity 50372..-- 120120 Sodium hydroxide, 50% aqueous solution 30 24 Soap (sodium stearate)10 10 Ammonium persulfate 9 4 .5 Water 2, 700 3, 300

The sodium hydroxide added was sufficient to provide a pH of about 9.1after cooking. The cooking was effected at about 260 F. in eachinstance, the coating composi tions emanating from the cooker, flashingto the atmosphere, the compositions then being at a temperature of about210 to 212 F. 1,782 parts by weight of oil (8.6. 0.78) were added ineach instance. In each instance water was added to an extent required toprovide a good operable viscosity on the laboratory blade coater foreach composition. The completed Composition A then, at a percent solidsof 28, had a viscosity of about 43 poises while Composition B, at apercent solids of 28, had a viscosity of about 90 poises. Each of thecompositions was applied to the usual paper web (one side) with alaboratory blade coater, dried in a blast of hot air and then lightlysupercalendered. Composition B exhibited a considerably higher viscosityindicating quite completely the effect of a very small amount of theoxidizing agent. However, both coatings were quite satisfactory and thecharacteristics of the coated webs are set forth in Table I.

10 EXAMPLE 7 The following example illustrates the formation of astarch-protein reaction product and of a coating composition utilizingonly a flour which contains both the starch and the protein. Thecomposition was formulated as follows:

Parts by weight Water 2700 The above coating composition was cooked at atemperature of approximately 260 F. and emanated from the cooker. Oilwas then added to the extent of about 1,782 parts by weight.Additionally, ammonia was added to provide the composition at a pH of9.5, water was added to provide in the coating composition percentsolids of 29.7 at a viscosity of 8,000 centipoises. The addition of theoil and water were made while the composition was hot F.) and vigorousemulsification followed the oil and water addition. The coatingcomposition was applied to a web in the usual manner, dried, lightlysupercalendered as in the foregoing examples, and the coated papercharacteristics for a one-side coated paper are as set forth in Table 1.

EXAMPLE 8 The following composition is illustrative of a coatingmaterial wherein the binder is present in materially lesser proportionby weight to the pigment than in the aqueous emulsion type coatingcompositions previously described. The composition is useful forletterpress and rotogravure printing particularly, and is in generaltypical of paper coating compositions. The formulation is as follows:

Parts by weight Clay (papermakers coating) 70 Sodium hexametaphosphate0.2 Calcium carbonate 30 Caustic 0.50 Starch, pearl corn (10% moisture)14.4 Protein, soya 1.6 Calcium stearate 0.14 Ammonium persulfate 9.0

Water suflicient to make 60% solids. Viscosity, about 5,000 centipoises.

TABLE I.-COMPARATTVE TEST RESULTS Example Ex. 3 Example Ex. 6 Example 12 A B 4 5 A B 7 8 810 61.3 49.4 51.8 48.5 43.4 43.7 44.6 45.6 36.2 57.4Bright-.- 73.4 73.0 70.5 69.8 70.3 69.7 71.0 70.2 68.9 69.3 Opacity.-.90.8 90.8 90.0 89.0 87.8 88.5 89.3 87.7 87.6 91.2 Half-tone test 1. 2.33.0 3.0 4.0 3.6 5.2 5.2 8.0 1.5 L/PPick 2.0 1.0 1.7 1.3 2.0 1.7 1.7 2.72.0 1.0 Rot0.conv 3.3 3.8 3.0 3.5 3.2 3.2 3.2 4.5 3.8 Dultgen 3.0 4.02.7 3.0 3.0 3.5 3.0 3.5 3.5 Coat wgt.

per 0118 side 4.8 3.0 3.5 3.5 3.0 3.4 2.5 2.4 2.0 12

In the foregoing description certain comparative tests have beenemployed to indicate the physical characteristics of the product. Theyare as follows: the gloss value is the percentage of specularlyreflected light reflected at an angle equal to the angle of incidenceemploying a black glass as a standard, the angle of incidence being 75and the area measured A" x 21; the higher the numerical value, thegreater the gloss. Brightness is measured with a GE. brightness testercommon to the art; higher values indicate higher brightness. Opacity ismeasured with the standard Bausch and Lomb opacimeter, the larger valuesindicating greater opacity. Letterpress half-tone is a print test and isa measure of the papers ability to reproduce 120 line screen with a 50%etch, the lower the numerical value the more suitable the paper for halftone printing, the range normally running from 1 to 10. The letterpresspick test is also a print test which involves printing of a solid bandof ink on the sheet under controlled conditions; the magnitude of pickor rupture during printing is graded against standard prints to attain anumerical value, and the lower th numerical value, the more pickresistant is the sheet and the more suitable is the sheet forletterpress printing. Rotoprintability is an indication of surfacelevelness as pertains to rotogravure printing and the test involvesactual printing of the sheets and comparison with standard prints,particularly for graininess in the print. The lower the numerical value,the more suitable is the print for rotogravure printing and the scalenormally runs from 1 to 10.

The foregoing examples illustrate the utility of the starch-proteinreaction product in coating compositions and a variety of ways in whichsuch coating compositions may be formulated. It is not believed to benecessary to specifically set forth other examples of usefultemperatures, common starches, proteins and flours. The effect of thehigh temperature, caustic and the oxidizing agent in combination is toreduce the degree of polymerization of both the starch and protein veryquickly. This apparently minimizes molecular aggregates and, by controlof the quantity of oxidizing agent introduced with relation to thetemperature, the degree of polymerization is reduced sufliciently toeliminate to a desired extent the high solution viscosities contributedby excessive molecular size. The oxidizing agents, particularly at hightemperatures, form the carbonyl groups on the starch while accomplishingthe uniform reduction in viscosity of the common starch-protein slurryand while retaining acceptable levels of adhesive strength. Theproduction of the carbonyl groups permits interaction with variousgroups of the protein, for example, amino groups.

In essence, it is considered that the oxidizing agent serves in theprocess to tend to reduce starch viscosity; however, even with a smallamount of protein present and with the oxidizing agent capable ofinducing carbonyl group formation on the starch molecules, a branchchain apparently results which restricts the reduction in viscosity.Such is beneficial as the product emanating from the cooker may then befurther altered as to viscosity characteristics if so desired.

While I have described my invention, particularly in connection with ajet cooker of the type wherein steam is introduced into the slurry toeifect cooking and agitation, such procedure is not necessary. Theflowing dispersion may be cooked in any suitable heating means such as asteam jacketed cooker wherein the mixing is eflFected mechanically. Infact, any dispersion mixing and heating equipment, steam heated,electrically heated, or otherwise is suitable.

Also, while I have particularly referred to sodium stearate and calciumstearate as useful soaps, any surface-active agent capable of complexingwith the amylose of the starch may be employed. Such other agentsinclude stearates such as those of ammonium and potassium, thepalmitates, myristates, petroleum base sulfonates, monoand diglycerides,aryl alkyl sulfonates, alkyl sulfonates and the like. Such agentscomplex with amylose to inhibit gelation and, where non-gelling isdesired, such a component is required when common starch is employed.The quantity of such surface-active agent should be sufficient toachieve a nongelling condition with the particular starch employed.

A plurality of advantages in the paper coating field result from thedescribed procedures: viscosity is readily controlled; water holdout onapplication to a Web is improved and the coating itself is well up onthe web surface; economy of production is attained and the coated paperproducts are of a desired nature, for the coating compositions thusachieved permit the production of very light weight printing papers.Light weight papers which are well adapted to printing are highlydesirable in the bookand publication fields. It is further to be notedthat the production of the light weight paper utilizing the describedcoating compositions is achieved without material loss of bulk and thatsupercalendering, while it decreases the bulk to some extent, is only alight application sufficient to assure a relatively smooth surface anddoes not deleteriously affect bulk properties.

The light basis weight coated printing paper, due t the evolution of theoil which follows the evolution of water from the coating composition onthe web, is provided with a multiplicity of pores or voids whichmaterially contribute to the opacity of the sheet even with lightcoating weights. This, as is known, is due to the air-coatinginterfaces. It is believed that, at these interfaces, the high bindercontent commonly contributes to a slight degree of tackiness in coatedpapers prepared from an emulsion system. It is quite unexpected that thestarch-protein complex would improve this characteristic.

In addition to the specific usages set out hereinbefore, thestarch-protein product has utility in varied fields. For these purposesthe relatively high viscosity materials emanating from the cooker may bediluted with water if desired. Such capabilities include usage infoodstuffs as stabilizers, i.e., chocolate milk; or in oil drillingmuds. It is my belief that I have discovered a new starch-proteinproduct and I intend to claim the same broadly as well as in the morespecific aspect of. the coating composition area.

It will be understood that this invention is susceptible to modificationin order to adapt to different usages and conditions and, accordingly,it is desired to comprehend such modifications Within the invention asmay fall within the scope of the appended claims.

What is claimed is:

1. In a process in which common starch in an aqueous alkaline slurrycontaining a water-soluble oxidizing agent capable of oxidizing starchalcohol groups to carbonyl groups is flowed through a heating and mixingzone and heated rapidly above the gelatinization range of the starchunder pressure with steam to a temperature in the range of about 220 F.to 350 F. to oxidize, swell, rupture and cook the starch to provide anaqueous dispersion, the steps of introducing into the aqueous alkalineslurry with the common starch and before heating the slurry, alkalinesoluble protein material to the extent of between about 5% to by weightof the total weight of starch and protein present to subject thealkaline soluble protein also to the oxidizing agent to substantiallycompletely exhaust the oxidizing agent and to cause the protein tointeract with the starch and achieve a grafting of protein and starchmolecules.

2. In a process according to claim 1 the step of introducing to theaqueous alkaline slurry about 0.1% to 5% by weight based on the weightof starch and protein an oxidizing agent selected from the groupconsisting of persulfuric acid and water-soluble per'sulfates and as theprotein material a protein selected from the group consisting of soyprotein and casein and to the extent of between about 5% to 10% of thetotal weight of starch and protein present.

3. A process according to claim 1 and which includes providing thestarch with the protein material to the aqueous slurry as a singlecomponent in the form of a flour.

4. In a process according to claim 1 and to provide the dispersion foruse as a binder in paper coating compositions, the steps of introducingthe protein material to the extent of between about to by weight of thetotal weight of common starch and protein material, adding to theaqueous slurry prior to the heating thereof sufficient water solublealkali to offset acidic products of hydrolysis of the proteinaceousmaterial, and also adding, at any time before the dispersion is cooledto the gelation range, an agent which forms a complex with amylose ofstarch to inhibit gelling of the dispersion, said agent being added tothe extent of between about 0.75% to 1.25% based on the dry weight ofthe starch and protein material.

5. In a process according to claim 4 and to provide the dispersion foruse in emulsion coating compositions, the step of emulsifying into thecomposition an oil having a vapor pressure which is less than that ofwater by adding such oil at any time prior to cooling of the compositionbelow about 180 F. and dispersing the oil with agitation into the formof small droplets having a diameter of between about 0.5 and 3 microns.

6. A fluid composition comprising an aqueous alkaline dispersion havinga pH in the range of about 8 to 10 containing the alkaline catalyzedreaction product at a temperature in excess of the gelatinization rangeof common starch of:

(a) common starch,

(b) protein to the extent of between about 5% and 85% by weight based onthe total weight of starch and protein,

(c) a water-soluble oxidizing agent capable of oxidizing starch alcoholgroups to carbonyl groups, and said composition including a complexformed between amylose of the starch and a starch gelation inhibitingagent whereby gelation of the composition is inhibited.

7. A fluid composition according to claim 6 for use as a paper coatingemulsion and wherein the composition contains oil and paper coatingpigment, said oil having a vapor pressure which is less than that ofwater and being emulsified in the composition in the form of smalldroplets having a diameter of between about 0.5 and 3 microns, thestarch gelation inhibiting agent being present to the extent of betweenabout 0.75% and 1.25% by weight and the protein being present to theextent of about 5 to 10% by weight based on the total of starch andprotein weights.

8. A fluid composition according to claim 6 for use as a binder in papercoating compositions wherein: the protein is present to the extent of 5to 10% by weight of the weight total of starch and protein, said watersoluble oxidizing agent is selected from the group consisting ofpersulfuric acid and water soluble persulfates, the starch gelationinhibiting agent is soap present to the extent of between about 0.75 and1.25% by weight based on the dry binder weight, and said compositioncontains oil and paper coating pigment, said oil having a vapor pressurewhich is less than that of water and being emulsified in the compositionin the form of small droplets having a diameter of between about 0.5 and3 microns, the composition having a solids content in the range of about25 to by weight and the Weight of oil present being at least equal tothe weight of the paper coating pigment.

9. A paper product having a dried printable coating thereon and whichcoating exhibits a multiplicity of cells contributing to the opacity ofthe coated paper, said coating being characterized by good pickresistance and improved resistance totackiness, said coating being thedried residue of a composition as claimed in claim 7.

10. A paper product as claimed in claim 9 and in which each side of theweb has a coating which is the dried residue of a composition as claimedin claim 7.

11. The alkali catalyzed reaction product of starch and protein inswollen and molecularly dispersed form in an aqueous alkaline dispersionat a temperature in the range of about 220-350 F. in the presence of awater-soluble persulfate oxidizing agent and an agent which forms achannel complex with amylose of the starch, the said protein beingpresent to the extent of between about 5-85% by weight of the totalweight of the starch and protein present.

References Cited UNITED STATES PATENTS 1,391,065 9/1921 Lenders.

3,372,050 2/1966 Weber.

2,400,402 5/ 1946 Evans.

2,059,343 11/1936 Hadfield 117156 2,360,828 10/1944 Craig 106-1572,776,226 1/1957 Hart 117165 2,900,268 8/1959 Rankin et al 106-1502,961,334 11/1960 Clancy et al. 117-l56 3,108,009 10/1963 Clancy et al.117--156 3,211,564 10/ 1965 Lauterbach 106214 JULIUS FROME, PrimaryExaminer.

T. MORRIS, Assistant Examiner.

6. A FLUID COMPOSITION COMPRISING AN AQUEOUS ALKALLINE DISPERSION HAVINGA PH IN THE RANGE OF ABOUT 8 TO 10 CONTAINING THE ALKALINE CATALYZEDREACTION PRODUCT AT A TEMPERATURE IN EXCESS OF THE GELATINIZATION RANGEOF COMMON STARCH OF: (A) COMMON STARCH, (B) PROTEIN TO THE EXTENT OFBETWEEN ABOUT 5% AND 85% BY WEIGHT BASED ON THE TOTAL WEIGHT OF STARCHAND PROTEIN, (C) A WATER-SOLUBLE OXIDIZING AGENT CAPABLE OF OXIDIZINGSTARCH ALCOHOL GROUPS TO CARBONYL GROUPS, AND SAID COMPOSITION INCLUDINGA COMPLEX FORMED BETWEEN AMYLOSE OF THE STARCH AND A STARCH GELATIONINHIBITING AGENT WHEREBY GELATION OF THE COMPOSITION IS INHIBITED.